Traditional technologies including liquid-liquid extraction (LLE) or solid phase extraction (SPE) are generally used as the pretreatment process to clean up or pre-concentrate the target species prior to chromatographic analysis of organic substances. However, these methods have certain drawbacks such as complicated operation processes, time consumption, high cost, health damage due to the usage of organic solvents, and the high expense with respect to the disposal of toxic organic solvents. Therefore, U.S. company Supelco introduced a solid phase microextraction (SPME) technology to overcome part of the above mentioned shortcomings of the traditional technology for preprocessing samples, and such technology can directly extract volatile and non-volatile compounds in a liquid or gas without using solvents or complicated apparatus, and also can directly analyze the sample by a gas chromatograph (GC) or a high performance liquid chromatograph (HPLC) with specific detector, including manual and automatic models.
Later on, the immersing SPME method was found being significantly influenced by the complicated matrix of sample. To improve this shortcoming, the headspace method (HS) technology was used with SPME as the HS-SPME technology in the sample pretreatment process for complicated matrix samples prior to the analysis in past years. However, HS-SPME sampling is only suited for volatile analytes, or it will take a long time to finish the sampling of targeting analyzed species from base bodies of samples having moderate sensitivity and reproducibility. The headspace sampling technique is thus limited to semi-volatile organic compounds and analyzed species with high boiling points.
Recently, microwave-energy was widely applied in the sample pretreatment process prior to chemical analysis such as accelerating sample digestion and solvent extraction of target species from sample. Through the dipole rotation and ionic conductance of polar substances or ionic species under the microwave irradiation, the temperature of the system rises within a very short-time period. Therefore, microwave heating has the potential to improve the HS-SPME sampling for organic compounds.